Video on demand (VOD) is a service that enables a consumer to request a program at a time that is most convenient to the consumer. VOD has proven to be popular with consumers for the flexibility and choices offered, and with service providers for the revenue generated. A viewer typically orders a VOD program by selecting a VOD program from an electronic programming guide displayed on a display device, such as a television or computer monitor. A user device, such as a set top box or a computer, processes the viewer's selection and initiates a request for the VOD program to the entity that provides the VOD service. This request may be serviced by equipment, in a service provider's network such as a headend that manages the distribution of programs, both VOD and broadcast, to a number of viewers. The headend is typically connected to many residences via a shared medium, such as a fiber or coaxial cable. In order for the headend to be able to provide the requested VOD program to the viewer, the medium must have sufficient available bandwidth to carry the VOD program. If the medium is at capacity and no available bandwidth exists, the headend must deny the request or delay providing the VOD program until sufficient bandwidth becomes available. In either event, the viewer is not as satisfied as if the VOD program had been provided instantaneously.
High Definition (HD) programming is becoming increasingly popular as consumers migrate from analog televisions to digital televisions. Unfortunately for service providers, a program encoded in HD typically uses more bandwidth than a program encoded in a lower resolution. Thus, HD programming increases utilization of the shared medium that connects the headend to multiple residences, decreasing the likelihood that sufficient bandwidth will be available to service VOD requests.
It is not uncommon for different viewers serviced by the same headend to request the same program at different times throughout the day. Currently, however, even when two viewers request the same VOD program within minutes of one another, a separate data stream of the VOD program is sent over the shared medium for each viewer. For example, during popular VOD usage times, such as on a weekend evening, there may be multiple requests for the same VOD program from separate viewers, each request requiring a separate data stream, and each request reducing the available bandwidth of the medium. Eventually the medium will become fully loaded and viewers' requests for VOD programs will go unfulfilled, increasing dissatisfaction among viewers and reducing revenue the service provider might have earned had more bandwidth been available. It would be beneficial to viewers and service providers alike if multiple viewers that initiate a request of the same VOD program at different times could share the same data stream of the VOD program.